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DIY ET-8 GOTO Mount

astrophotography eq mount
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#101 ssagerian

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Posted 26 February 2015 - 10:50 AM

Just a minor update, if you want to hook up the limit and PEC functions. You need to make or have someone make a cable for each.

 

 

The connector and the pins that go into the connect are as follows (these are digikey part numbers)

 

HALL PEC connector is  455-1126-ND  here is the link http://www.digikey.c...-1126-ND/527357

 

for each wire, you need to crimp/solder a crimp terminal 455-1127-1-ND  ( you will 2 for the limit switch, 3 for the HALL effect sensor, I suggest buying 10 or more) here is the link http://www.digikey.c...127-1-ND/527358

 

LIMIT switch connector is 455-1165-ND http://www.digikey.c...-1165-ND/608607

 

The crimp terminals are crimped on to the wires and then inserted into the housing. the completed connector is inserted in the on board connector.



#102 Geo.

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Posted 26 February 2015 - 12:32 PM

Hey, a little peek at Steve's sweatshop :bow:



#103 photo444

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Posted 26 February 2015 - 05:02 PM

Steve,

 

Thanks for the info.

 

Paul



#104 pbunn

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Posted 03 March 2015 - 01:15 PM

Is there somewhere that has a step by step for loading the on step software into the Ardinuo board. I have no experience with them. I am sure that it is simple.

 

Pat



#105 orlyandico

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Posted 03 March 2015 - 01:37 PM

so PEC requires an indexer? many stepper mounts don't need/use an indexer. also if the indexer is present, does the controller seek the indexer? or is PEC recording/playback disabled until the index is seen?



#106 photo444

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Posted 03 March 2015 - 01:51 PM

Hi Pat,

 

I trying to recap my memory.

1. Go to https://github.com/hjd1964/OnStep and from the branch (left side of the screen) select Dev branch.

2. Click on Download ZIL located lower right of the screen.  This will download the ZIP package.

3. Unpack the zip file to your directory, Files will be unpacked in to a directory "OnStep-Arduino-Mega2560-Teensy 3.1-Dev".  You may directly unzip to a directory name "OnStep", alternatively.

4. Rename the directory to "OnStep".  This is important to match the .ino file name in the directory.  OnStep.ino is the main file.

5. Run Arduino

6. Open "Config.h" and edit parameters that  are relevant to your mount.

7. You are all set to compile.  I assume you know the basics of Arduino.

 

I have chosen Dev branch because it is easy to edit mount parameters for my drive.

 

Good luck,

 

Paul 



#107 pbunn

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Posted 03 March 2015 - 05:03 PM

I am not fluent in Arduino but have played with it. Never have compiled a program.

 

Pat



#108 Geo.

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Posted 03 March 2015 - 05:32 PM

Steve if you have any troubled with parts I do have a lathe and it's almost warm enough again for me to spend some time in the shop!  Let me know.



#109 Geo.

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Posted 03 March 2015 - 05:44 PM

I am not fluent in Arduino but have played with it. Never have compiled a program.

 

Pat

Get isbn: 978-1-449-30987-9 at Amazon, $2.99 up. Arduino speak is really not much different than other high level code. It just uses some different terminology to aid the right-brained. I'm more familiar with PicMicro assembly code, not the same. but it rhymes. 



#110 pbunn

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Posted 03 March 2015 - 06:58 PM

Yes, I have done Intel assembly since the late 70s and moved to PIC assembly. I did a PIC article in QST in the early 90's using it as a Morse code keyer.

 

Never used much C or other higher level stuff. I have a decent book (I think) Programming Arduino by Simon Monk.  I'll learn what I have to. I just ordered your recommendation from Amazon.

 

More a hardware person than software.

 

Pat


Edited by pbunn, 03 March 2015 - 07:02 PM.


#111 hjd1964

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Posted 04 March 2015 - 11:15 AM

Good questions Orly:

 

"so PEC requires an indexer?"

No.

 

"also if the indexer is present, does the controller seek the indexer?"

No.

 

PEC uses a "soft" index and an index offset.  If index support is enabled, that index offset will be noted when the index arrives during playback and recording.  The new index offset will take effect after the current sequence is complete.

 

Recording waits for the "soft" index, playback always starts immediately.

 

I'll be revisiting PEC and index support and will be making improvements in the future.  One obvious improvement would be to allow Index detection during gotos, this should get the critical first detection done before any recording/playback happens.  I specifically attached the hall-sensor signal to an external interrupt enabled pin of the MCU for this reason.  The other improvement would be to allow recording to start immediately, this is a bit tricky and I had that working at one point but then changes broke it so I disabled the feature rather than trying to tackle that and add index support all at once.

 

PEC looks simple on the surface, but I've found it tricky to implement and very time consuming to test.

 

OnStep has been steadily improving and especially over the last year or so has started to reach a fairly refined state, but it's still in Beta and there are bugs and shortcomings.  Some things are easily fixed/added with confidence and they immediately make there way to the Dev branch on GitHub.  Others are of a more subtle nature and require testing under the stars to confirm that more good than harm is being done.  The current experimental version allows goto rate setting in the ASCOM setup dialog, changes rate generation to fixed point math, lowers jitter during sidereal tracking, adds initial support for fork mounts, etc. 

 

Of these the rate generation fix is the most important, I never noticed this on my mounts, but testing a wide range of configurations showed the problem.  The fix is a much better all around way to do the same thing, and the same tests say it's all working perfectly, but I need to do some testing under the stars to make sure the rate generation is exact.

 

As always, I welcome feedback (bugs/improvements/features) and try to fix problems quickly once identified so stay in touch via my email (available on my site) or post here.


Edited by hjd1964, 04 March 2015 - 02:03 PM.


#112 hjd1964

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Posted 04 March 2015 - 12:26 PM

Hi Pat,

 

I trying to recap my memory.

1. Go to https://github.com/hjd1964/OnStep and from the branch (left side of the screen) select Dev branch.

2. Click on Download ZIL located lower right of the screen.  This will download the ZIP package.

3. Unpack the zip file to your directory, Files will be unpacked in to a directory "OnStep-Arduino-Mega2560-Teensy 3.1-Dev".  You may directly unzip to a directory name "OnStep", alternatively.

4. Rename the directory to "OnStep".  This is important to match the .ino file name in the directory.  OnStep.ino is the main file.

5. Run Arduino

6. Open "Config.h" and edit parameters that  are relevant to your mount.

7. You are all set to compile.  I assume you know the basics of Arduino.

 

I have chosen Dev branch because it is easy to edit mount parameters for my drive.

 

Good luck,

 

Paul 

 

That looks good Paul.  I definitely recommend using the Dev branch of OnStep too.  Even though the stable branch doesn't suffer from the rate generation problem mentioned above, it's performance in other ways/features are getting fairly far behind the Dev branch now.  The rate gen. issue may or may not be present anyway, depending on your configuration, and even if present you might not even notice since it only seems to show itself at specific low guide rates (0.25x, 0.5x.)

 

Other "Required" reading that might help, in addition to Config.h:

http://www.stellarjo...quipment_onstep



#113 orlyandico

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Posted 04 March 2015 - 12:36 PM

one other suggestion regarding PEC.. not sure if this is already implemented.

 

it would be good if the PEC recording automagically normalizes / removes drift once the worm cycle is complete.  That will remove systematic drift due to polar misalignment in altitude or due to refraction.

 

also... some sort of interpolation / curve-fitting routine to smooth out the spikes (a simple low-pass filter across say +/- 5 PEC cells).  But a low pass filter phase-shifts the output, so it would be a good idea to phase-shift the LPF output (just by shifting the index count left) to get rid of the phase delay.

 

i know these are things that are arguably better off done from a utility, but there's a certain simplicity to it being transparently done when you do a PEC training via ST-4.



#114 hjd1964

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Posted 04 March 2015 - 01:09 PM

one other suggestion regarding PEC.. not sure if this is already implemented.

 

it would be good if the PEC recording automagically normalizes / removes drift once the worm cycle is complete.  That will remove systematic drift due to polar misalignment in altitude or due to refraction.

 

also... some sort of interpolation / curve-fitting routine to smooth out the spikes (a simple low-pass filter across say +/- 5 PEC cells).  But a low pass filter phase-shifts the output, so it would be a good idea to phase-shift the LPF output (just by shifting the index count left) to get rid of the phase delay.

 

i know these are things that are arguably better off done from a utility, but there's a certain simplicity to it being transparently done when you do a PEC training via ST-4.

 

From Config.h:

 

// enables code to clean-up PEC readings after record (use PECprep or a spreadsheet to fix readings otherwise)
// this cleans up any tracking rate variations that would be introduced by recording more guiding corrections to either the east or west, default=ON
#define PEC_CLEANUP_ON

 

A low-pass/smoothing filter is on my to-do list.  Which reminds me, I should mention that PEC recording operates in two modes.  If you send the command to clear the buffer the next record will simply drop 100% of the corrections into the PEC buffer.  If you record again without clearing the buffer, recorded values are combined in a weighted average 3:1 favoring the buffer.

 

FYI, the buffer works with one second intervals, and playback is shifted one second ahead of record.

 

Recorded values are held in ram.  Tracking must be stopped (park or home the mount) and the write PEC data to EEPROM command issued for the values to be remembered.  This avoids serious timing problems when writing to EEPROM directly (while recording PEC) and also allows you to evaluate the results of a recording session without committing to destroying any prior data.

 

OnStep has no ST4 support, but really it would be trivial to add, I just have no use for it and no one has asked.



#115 orlyandico

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Posted 04 March 2015 - 02:03 PM

ah ok so guiding is implemented with PulseGuide.  a good idea, ST-4 support will require an additional piece of hardware (an optoisolator) and 4 I/O pins.

 

How often is the PEC table stored to EEPROM?  ideally this should be automatic, but should also be not too frequent to avoid wearing out the RAM...  (at the very least, without an indexer, the PEC index must be written to the EEPROM every now and then to avoid synchronization issues)

 

of course if there is an indexer, this requirement becomes significantly relaxed.

 

since you say the PEC happens every second, so the number of PEC cells is not fixed?  how do you allocate EEPROM space for a variable-size PEC table?

 

IMHO the correct PEC table size would be somewhere between 88 (Celestron) and 1100+ (Astro-Physics). Honestly I think the AP value is overkill.  In my experience it's best to just load the fundamental, for which a 128-cell table (give or take) is sufficient.

 

does the ASCOM driver support direct PEC upload/download?  it would be great if we could support PEMPro direct upload/download - training via pulse guide gets old really fast.

 

anyway when I get my board I can start contributing to the code as well.



#116 pbunn

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Posted 04 March 2015 - 03:20 PM

I downloaded the zip file and unzipped it to a folder named "on step" and I see the Config.H file.

 

When I run Arduino -  and select open  -I load onstep.ino

 

 

The configuration file seems to be properly set with default values.

 

When I select verify - I get a long series of errors with many values undeclared. As I said - I do not have any experience with Arduino. It appears that I am not loading all of the program. Do I load all of the ino files?

 

 

Pat


Edited by pbunn, 04 March 2015 - 03:34 PM.


#117 photo444

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Posted 04 March 2015 - 04:00 PM

Pat,

 

The folder name OnStep has to match with the file name OnStep.ino. Otherwise you will get error. Once you open Arduino, set the board to Mega 2560, click File/open then select your directory OnStep\OnStep.ino.  You will see another window opens and file tabs are displayed on the top portion. Then you can edit individual files at a time.

 

Paul



#118 hjd1964

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Posted 04 March 2015 - 05:46 PM

ah ok so guiding is implemented with PulseGuide.  a good idea, ST-4 support will require an additional piece of hardware (an optoisolator) and 4 I/O pins.

 

How often is the PEC table stored to EEPROM?  ideally this should be automatic, but should also be not too frequent to avoid wearing out the RAM...  (at the very least, without an indexer, the PEC index must be written to the EEPROM every now and then to avoid synchronization issues)

 

of course if there is an indexer, this requirement becomes significantly relaxed.

 

since you say the PEC happens every second, so the number of PEC cells is not fixed?  how do you allocate EEPROM space for a variable-size PEC table?

 

IMHO the correct PEC table size would be somewhere between 88 (Celestron) and 1100+ (Astro-Physics). Honestly I think the AP value is overkill.  In my experience it's best to just load the fundamental, for which a 128-cell table (give or take) is sufficient.

 

does the ASCOM driver support direct PEC upload/download?  it would be great if we could support PEMPro direct upload/download - training via pulse guide gets old really fast.

 

anyway when I get my board I can start contributing to the code as well.

PEC data isn't written automatically to EEPROM, I really didn't want to go that way.

 

EEPROM endurance is >100k writes, so I don't worry much about once or twice per session writes.  With or without a PEC index sensor, the soft index is written on every park.  You must park to preserve the index unless you have an index sensor.

 

 I divided up EEPROM into three areas, a data/settings area, the PEC table area, and an reserved area.  There's an initialization stamp and code that lets OnStep know if initialization has taken place so first-time uploads on new hardware auto-init. the EEPROM.

 

Not sure what you mean about the PEC table allocation not being fixed... for a given configuration it is fixed.  For any worm drive there are a certain number of seconds per worm rotation.  In my system each second indexes into the PEC table.  At the soft index (step based) the sequence begins again.  Guide corrections (if applied) can push the worm a little this way or that, and I don't have this factored into the buffer playback position.  My thought is that the guide corrections will generally be small enough to not disturb the PEC playback significantly.

 

As for table size, I choose the PEC table layout because it fit the design.  A one-second slot allows me to use a signed 8-bit value which is a nice fit with the 100 steps per second limit (since I'm recording steps for +/-1x sidereal guide rate max, that's +/-100) which in turn is a nice fit for a reasonable arc-seconds per micro-step range (15/100=0.15 arc-sec/step) that hopefully is adequate for most everyone.  This fits with the 0.01 sidereal second timer interrupt in OnStep that ultimately governs the targetHA/Dec during tracking/guiding.  The main-loop of OnStep is designed so it always completes faster than this sidereal timer and moving the targetHA/Dec for tracking/guiding/PEC are all based on the 0.01 second intervals.  The motor timers then run in the background at as close to the exact rate required as practical (for the RA rate, a sum of PEC + guide + sidereal) to smooth all of this out on the way to becoming step pulses to the drivers.

 

The ASCOM driver doesn't support PEC upload/download.  I choose to implement this feature in my planetarium software which also shows a "live view" of the PEC data, indexes, etc.  You can have a copy of the ASCOM driver source if you feel inclined to implement it or I can throw something together over the next month or so.  I doubt all of the PEC commands are documented on my site, but the source should be clear (it's in command.ino.)


Edited by hjd1964, 06 March 2015 - 04:02 PM.


#119 pbunn

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Posted 05 March 2015 - 07:53 PM

OK

 

I think I have loaded and compiled the OnStep program. When I powered up the Arduino board with the driver board on top - I get a red LED on the RA side and a flashing blue LED under the Bluetooth module.

 

I uploaded the compiled code and the red LED went off , but the flashing blue LED continues.

 

I have nothing connected to the board except the USB connection

 

What is a simple way to verify that the program loaded and is working. I have not loaded the ASCOM driver, and I assume that I should do that and then attempt to connect with a planetary program. How far off the mark am I.?

 

 

Pat



#120 photo444

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Posted 05 March 2015 - 09:20 PM

Pat,

 

If you have a mount that has stepper motors then you are not that far off.

 

With the usb connected to the Mega board, you can check the program. From the Arduino IDC, go to the serial Monitor on the tools menu.  You can send LX200 commands by typing and get the responses.  

http://www.stellarjo...tware_telescope shows the commands you can try.

 

If you have android phone, you can run the OnStep Telescope Control App after download.

 

Have fun!

 

Paul



#121 ssagerian

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Posted 05 March 2015 - 09:47 PM

The blinking Blue light is the blue tooth control software indicating its not "paired" with another device, if you use the android app, you can "pair phone with the board"  by entering the boards mac address, 

go to the top right corner of the app and click on the three vertical dots, that will bring up a menu with "Bluetooth Address" as the second to last item,

select that and enter your bluetooth address (its printed on the bluetooth module). should be 6 octets with colons in between 00:06:66:6E:8C:AB (for example)

 

in upon which the blue light will turn on solid (stop blinking but still be on.

 

You guys are great the way you help each other out. Keep up the sharing..



#122 pbunn

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Posted 05 March 2015 - 09:48 PM

Pretty sure that it is working as the ASCOM connected and disconnected from the board.  I don't have an Android tablet. Is there an application that will run on a PC to run the mount? Or some other method like a PC program that is similar to the Android App. Does it connect to a C running a planetarium program? 

 

I have a Losmandy GM 8 that has steppers - also some other mounts that I can mount steppers on.

 

I see that there are quite a few Androids tablets  that are low priced. Is this the best way to operate the mount as a goto mount? Anything special in the Android Tablet that I need? Sorry for so many questions.  I have Apple stuff rather than Android. I think my son won an Android Tablet in a raffle last year that I might be able to grab.

 

Thanks - I think this is going to be fun.

 

 

Pat


Edited by pbunn, 05 March 2015 - 09:49 PM.


#123 orlyandico

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Posted 05 March 2015 - 09:59 PM

Just use Cartes du Ciel or any similar PC app, and connect to the ASCOM driver.

 

The Android device is so that you can use the mount without a PC.



#124 Gary.McK

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Posted 06 March 2015 - 02:04 AM

Hi,

 

I'm having a bit of rouble getting smooth steeper rotation....I get a cyclic sound when tracking and a small clunk when it reaches a full step position. Have tried both 16 and 32 microsteps at varying voltages up to 24 volts - the clunk is worse at higher voltages.

 

I can get smoother rotation at 12 volts and a high amperage setting, but then the motors get warm.... I have also found that the tepper driver chips ae getting very hot - should I put some heatsings on them?

 

Any ideas for smooth rotation?

 

cheers

Gary



#125 hjd1964

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Posted 06 March 2015 - 05:05 AM

Pretty sure that it is working as the ASCOM connected and disconnected from the board.  I don't have an Android tablet. Is there an application that will run on a PC to run the mount? Or some other method like a PC program that is similar to the Android App. Does it connect to a C running a planetarium program? 

 

I have a Losmandy GM 8 that has steppers - also some other mounts that I can mount steppers on.

 

I see that there are quite a few Androids tablets  that are low priced. Is this the best way to operate the mount as a goto mount? Anything special in the Android Tablet that I need? Sorry for so many questions.  I have Apple stuff rather than Android. I think my son won an Android Tablet in a raffle last year that I might be able to grab.

 

Thanks - I think this is going to be fun.

 

 

Pat

 

My Android App or Sky Planetarium are recommend since one or the other is required to get through the align sequence.  The Android device is really handy if doing visual observing since it can be used at the eyepiece for centering objects.  I'd try an Android >= version 4.0 phone or table but keep in mind that it needs to have bluetooth and whatever device you choose should support downloading apps from the google play store otherwise installing my app gets more complicated.  I like tablets since things like Sky Safari are a bit tedious on a phone.




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